In the group of subjects, there was a strong correlation between the severity of fetal anemia (MoM-Hb) and both, NT-proBNP values (R = − 0.64, p < 0.001) as well as MoM-MCA-PSV values (R = − 0.50, p < 0.001). The gene discussed is GSTM1; the disease is anemia (phenotype).